In the coming grant period we plan to: 1. complete and publish the call-threshold maps of the midbrain. These provide evidence for functional subdivisions of a brain region that is relatively homogeneous. We will also complete the degeneration studies of inputs to midbrian from archistriatum and diencephalic regions involved importantly in calling, and of outputs of the intercollicular and ventral division of the lateral mesencephalic nucleus. The degeneration results are already giving us better interpretations of results from small differences in placement of stimulating, lesioning and recording electrodes. Our major efforts this year will be to determine 1. how the midbrain structures control medullary call units, and 2. what the role(s) of the midbrain structures is (are) by analyzing midbrain unit responses to inputs from other brain areas and to sensory stimulation. In (1) we will attempt to distinguish call-related medullary activity form other systems activated by the ESB electrode by comparing pre-curarized refractory periods (pulse-pair intervals) with those for medullary units in the curarized preparation.